Executive federalism emphasizes collaboration between the executive branches at the national and state levels to transform grant programs through the implementation process. In this regard, Medicaid demonstration waivers loomed large during the presidencies of Bill Clinton and George W. Bush. This article documents and compares the volume and substance of section 1115 Medicaid waiver activity under the two presidencies. From the perspective of policy performance, Medicaid demonstration waivers provide modest support for the view that states serve as laboratories for policy learning in the health care arena. More broadly, the waivers have not yielded a major solution to the problem of the uninsured and are unlikely to do so. At the same time, they have not (as some have suggested) been a subterranean force for the erosion of Medicaid. To the contrary, these waivers have often enhanced health services for low-income people; above all, they have helped preserve Medicaid as an entitlement by undercutting support for those seeking to convert the program into a block grant. From the perspective of the democratic process, we find that Congress has been a more significant player in shaping waivers than the executive federalism model suggests. While the decision processes surrounding Medicaid waivers often fall short of democratic standards with respect to transparency and opportunities for public input, they still compare favorably to certain alternatives.